For a magnetic tape such as a video tape or an audio tape, either a so-called coating type magnetic recording medium or a metal thin-film type magnetic recording medium is proposed. That is, according to the former, a magnetic coating material, which is prepared in such a manner that a powdery magnetic material, a binder, and various additives are dispersed and kneaded together with an organic solvent, is coated on a non-magnetic support member and then dried. According to the later, a magnetic layer is formed in such a manner that a metal magnetic material is directly coated on a non-magnetic support member by using a vacuum thin film forming technique.
In this case, a recording/reproducing operation of an information signal with respect to each of these magnetic tapes is performed while the magnetic layer side of the magnetic tape is slidably moved on a magnetic head. For this reason, if surface projections are unexpectedly formed on the magnetic layer surface of the magnetic tape, the surface projections are sheared and broken by slidably moving between the magnetic head and the magnetic tape and are interposed as a fine magnetic powder (to be referred to as an abrasion powder hereinafter) between the magnetic tape and the magnetic head. The abrasion powder interposed between the magnetic tape and the magnetic head causes dropouts, for example, causes image degradation, sound skipping, or the like and, in the worst case, causes head clogging to make it impossible to record/reproduce data.
Therefore, in a conventional magnetic tape described above, a magnetic layer is formed on a non-magnetic support member, and then subjected to a surface process in which the magnetic layer surface is polished with a magnetic tape. A polishing apparatus for performing the surface process is shown in FIG. 1.
The polishing apparatus 101 has a polishing tape 103 and a contact roll 102, having a diameter of about 30 mm, for pushing the polishing tape 103 against the a magnetic tape 104.
The polishing tape 103 is wound on the contact roll 102 at an arbitrary holding angle to cause its polishing layer to face outside. The holding angle of the polishing tape 103 wound on the contact roll 102 is controlled in such a manner that the polishing tape 103 is looped between a pair of winding rolls 105a and 105b arranged parallel to each other near the contact roll 102.
Guide rolls 106a and 106b are arranged on both the sides of the contact roll 102 on which the polishing tape 103 is wound, respectively. The guide rolls 106a and 106b are used to guide the continuously traveling magnetic tape 104 to a position where the magnetic tape 104 is brought into contact with the polishing tape 103 wound on the contact roll 102.
In this polishing apparatus 101, a feeding roll and a take-up roll (not shown) are arranged for each of the polishing tape and the magnetic tape. The end portions of the polishing tape 103 are attached to the feeding roll and the take-up roll, respectively, and the end portions of the magnetic tape 104 are attached to the feeding roll and the take-up roll, respectively.
In the polishing apparatus 101 as described above, when the feeding roll and the take-up roll for the polishing tape and the magnetic tape are rotatably driven, the polishing tape travels in an X direction in FIG. 1, and, in contrast to this, the magnetic tape travels in a Y direction in FIG. 1. In this manner, the magnetic layer surface of the magnetic tape is polished by the polishing tape, and the surface projections on the magnetic layer surface are cut and removed.
However, in the polishing apparatus, when the magnetic tape and the polishing tape are traveled in opposite directions, respectively, air is inserted between the magnetic tape and the polishing tape to form an air film, and the magnetic tape is in incomplete contact with the polishing tape. For this reason, the magnetic layer surface cannot be sufficiently polished by a single process. When a high-quality magnetic tape is to be manufactured, the surface process must be performed a plurality of times to sufficiently polish the magnetic layer surface. Since the thickness of the air film formed between the magnetic tape and the polishing tape increases with a process speed, a process speed is limited to bring the magnetic tape and the polishing tape into sufficient contact with each other. Therefore, the process speed cannot be easily increased. For these reasons, a sufficiently long period of time is required to perform the surface polishing process, thereby preventing productivity of magnetic tapes from being improved.